A huge number of the world's population wears eyeglasses in some form. The term “eyeglasses” generally refers to a device in which lenses are worn in front of the eyes, including but not limited to: spectacles for vision correction; sunglasses for solar protection and safety glasses for eye protection.
Eyeglasses generally comprise a frame for bearing the optically transparent lenses and positioning them appropriately in front of the eyes of the wearer. The frame of eyeglasses generally comprises at least some of the following components: rims to which the lenses are attached; arms or temples which are placed over the ears of the wearer; and a bridge which connects the two lenses (or their rims) together. Part of the frame, typically but not always the bridge, is adapted to rest on the nose of a wearer.
Eyeglasses have evolved over the years from being a purely functional item to being a fashion accessory. The style of eyeglasses has evolved accordingly, in terms of their shape, size and colour. Nowadays, people often desire to have more than one pair of eyeglasses to suit use in different situations, to complement different outfits or simply for the sake of variety. However, the high price of eyeglasses prevents this being a practicable option for many people.
One way in which the style of eyeglasses can be varied relatively cheaply is with interchangeable parts. For example, US 2006/0139567 describes eyeglasses having detachable temple arms so they can be changed by a user. The temples disclosed in this document include recesses that can rotate around pins on lens connectors. U.S. Pat. No. 7,029,115 discloses similar eyeglasses to US 2006/0139567. A temple arm is detachable from pins on lens connectors upon relative motion of the temple arm parallel to the temple arm or in a direction less than 45° to it. The temple arm can be detached from the rest of the eyeglasses when the temple arm is in any configuration, provided a force is applied in the appropriate direction. In both these documents, the pins of the lens connectors need to be deformed to be both inserted into the recesses (to connect the temple arms) and removed from the recesses (to remove the temple arms). This makes connecting and removing the temple arms a fiddly task and the need to deform the pins means they are susceptible to breakage. Even so, the ability to disconnect temple arms when they are in any configuration may result in accidental disconnection.
In other prior art temple interchange systems, the temple arms can become detached too easily, which is clearly undesirable.
WO 95/13558 describes eyeglasses having interchangeable lenses for varying the type of lens according to the requirements of the situation, for example for long distance or short distance viewing, or for protecting from the glare of the sun. The lenses may also be used with eyeglass frame parts of a different colour or style.
U.S. Pat. No. 7,712,894 discloses eyeglasses with detachable temple arms and a slit in the frames proximate the point of connection with the temple arms to allow the lenses to easily be removed. The slit is formed between two parts of the frames that each has a pivot pin for engaging with a hooked part of the temple arm to allow rotation of the temple arm. The temple arm is detachable from the frame upon movement of the temple arm relative to the frame so that the pivot pin slides along a slot in the temple arm and can pass through an opening. In the closed or folded configuration, the temple arms can be very easily detached from the frames, which may be undesirable.
Other known eyeglasses have temple arms attached to the frames by means of small screws. These are prone to becoming loose, requiring tightening with a small screwdriver. The need for screws adds an extra component and complexity to the manufacturing process.
These prior art systems do provide some ability to change the style and colour of eyeglasses, but the degree of customisation that is possible is limited. For example, the ability to change the bridge and temple arms only allows the style of eyeglasses to be changed only to the extent allowed by changes in the style of those parts.
Furthermore, prior art eyeglass systems having interchangeable parts have been found to be weaker and more flimsy than is desirable for a product designed for long-term use. This is especially true at the join of interchangeable parts, such as where temple arms are pivotally connected to the frames or lenses.